This invention relates to an automatic sheet feeding system of a printing apparatus comprising a printing head disposed on the front side of the platen for movement axially thereof, and a sheet ejecting stacker and a sheet feeding stacker arranged one above the other in the indicated order from above rearwardly of the platen.
A known automatic sheet feeding system of the type described above comprises a sheet feeding roller of the sheet feeding stacker and a sheet ejecting roller of the sheet ejecting stacker arranged adjacent the platen, wherein the platen is driven by the drive of the printing apparatus or by a built-in motor and rotation of the platen is transmitted to the sheet feeding roller and sheet ejecting roller via a clutch.
In the known automatic sheet feeding system referred to hereinabove, the platen is already rotating when a sheet on the sheet feeding stacker is fed by the sheet feeding roller. If the sheet fed is not in a regular position but in a tilting position, for example, then the sheet is mounted in the tilting position on the platen and printing is carried out on the sheet which is not in the regular position. Correction of the sheet in an irregular position requires special parts and renders the sheet feeding system complex in construction.
In the aforesaid type of automatic sheet feeding system, it is well known that difficulties are encountered in setting the printing initiating position on a sheet at a predetermined distance from the leading edge of the sheet. It is necessary to detect, in the aforesaid automatic sheet feeding system, whether or not a sheet has been fed on the platen, and the detecting device is arranged at the inlet of a sheet ejecting passage adjacent the platen so that such device may not interfere with checking of the printed letters or manually feeding of a sheet. When the leading edge of a sheet is detected by the detecting device, the desired printing initiating position would have already passed by the printing means. Thus if printing were carried out in this condition, a large blank space would be present on the sheet between the leading edge of the sheet and the position in which printing is actually started or an unprintable zone of a large area would be formed in the upper margin of the sheet.
Additionally, in the aforesaid automatic sheet feeding system, when a sheet is fed manually, it is necessary to remove the automatic sheet feeding system as a whole from the sheet feeding section of the printing apparatus. This operation is troublesome.